The present invention relates to a security system for a broadcast environment, and more particularly to such a system which defeats eavesdropping.
This invention relates to an electronic security system that addresses the security issue in the broadcast environment: transmitter (including transceiver acting as transmitter) to receiver (including transceiver acting as receiver). A broadcast signal, once sent by a transmitter or transceiver, is recognized by a receiver or transceiver, which appropriately responds to it. Since the environment is a broadcast environment, eavesdropping is phenomenally easy and relatively undetectable. The broadcast signal eavesdropped upon can be recorded and then replayed at a later time by the eavesdropper at his volition. Hence, that which is radio-transmitted or broadcast is no longer private information. The only solution is for the broadcast signal to have a private part, which is discarded after use, since the private part maintains its privacy until it is used.
In the general view, the receiver (whether it be exclusively a signal receiver or one transceiver of a communicating pair) grants access to a site, information, or functional capability, upon receipt of a valid signal, so we shall call it the "access grantor" (i.e., the lock). The transmitter (whether it be exclusively a signal transmitter or the other transceiver of the communicating pair) transmits a signal (a packet of data) to the receiver ("access grantor") requesting access to a site, information, or functional capability, so we shall call it the "access requestor" (i.e., the key).
Among the many possible applications for an electronic key are radio-transmitter electronic garage door opener, remote car locker/unlocker or starter, replacements for standard keys and locks, cordless phones (to protect access to a phone line from an unauthorized cordless phone), wildlife researchers' radio-transmitter collars, and so on.
The current crop of radio-transmitter electronic garage door openers and the like easily succumb to even a semi-intelligent attack. There are so few possible "code" signals available (typically about 512 for a given frequency) that a computerized brute force try at all of them can be done in a very short time using a computer. Even increasing the number of possible "code" signals available will not help, since it is relatively easy for an eavesdropper to record the signal when the proper user transmits it to perform the designated function (e.g., to open or close the garage door); it can then be played back at any later time at the eavesdropper's volition.
Accordingly, it is an object of the present invention to provide a security system which cannot be defeated by eavesdropping.